Category Archives: Stuck Pipe

Key Seat Causes Stuck Pipe

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While drilling, with high tension and torsion in a drilling string, the drill string creates wear, called “key seat “ at wellbore where there are changes in the direction. The soft to medium hard formation has a great tendency to get key seat. While pulling out of the hole, BHA gets stuck into the key seat.

Key Seat

Key Seat

Warning signs when you get stuck due to Key Seat

  • High dog leg severity
  • Long drilling hours without reaming back through the high dog leg area

 Stuck identification for Key Seat

  • This situation occurs when pulling out of the hole only.
  • Circulation is not restricted.
  • High over pull is suddenly seen when the BHA is pulled into the key seat.
  • Tripping back is possible.

 What should you do for this situation?

  1. Because the drill sting gets stuck while moving up, jar down with maximum trip load, which must be applied. Torque while jarring down can be applied as well.
  2. Bring the rotation at a slow speed and attempt to ream back with a small over pull into the key seat areas.

 Preventive actions:

  1. Do not try to drill with a lot of dog leg severity
  2. Back ream some areas where high dog leg severity is presented.
  3. Run a short trip or wiper trip to minimize the key seat.
  4. Utilize a reamer in high dog leg zones.

References

John Mitchell Drilbert Engineering, 2002. Trouble-Free Drilling Volume 1: Stuck Pipe Prevention. Edition. Drilbert Engineering Inc.

Fanarco.net. 1999. Stuck Pipe Prevention Self-Learning Course. [ONLINE] Available at: http://www.fanarco.net/books/drilling/stuck-pipe.pdf. [Accessed 21 June 2016

Steve Devereux, 2012. Drilling Technology in Nontechnical Language, 2d Ed.. 2 Edition. PennWell Corp.

 

Soft Cement Causes Stuck Pipe

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The drill string/BHA is in soft cement and when circulation is established, pumping pressure causes the soft cement to flash set (cement becomes harder quickly). Finally, the drill string gets stuck due to the hard cement around it. The diagrams below demonstrates the process of flash set cement.

BHA in Soft Cement

BHA in Soft Cement

Turn the pump on while BHA is in the soft cement

Turn the pump on while BHA is in the soft cement

Soft cement becomes flash set

Soft cement becomes flash set

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Cement Blocks Causes Stuck Pipe

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Cement around a casing shoe or open hole cement squeeze becomes unstable and finally, chunks of cement can fall into a wellbore. If there are a lot of cement chunks in the annulus, the drilling string will get stuck.

Cement Blocks

Cement Blocks

 Warning signs when you get stuck due to Cement Blocks

• Rat hole is too long.

• Drilling into areas where open hole cement jobs as cement squeezes or kick off plug was performed.

Stuck identification for Cement Blocks

• Cement chunks are seen at shale shakers.

• There is cement content in mud logger samples.

• Stuck pipe due to cement blocks can  occur anytime.

• Circulation is not restricted.

• Torque and drag are drastically increased and erratic.

What should you do for this situation?

1. Stuck while moving up, jar down with the maximum allowable trip load. Gradually apply torque if required.

2. Stuck while moving down, jar up without applying torque.

3. Pump weighted hi-vis sweep with maximum allowable flow rate to clean large pieces of cement from around drilling string/BHA.

Preventive actions:

1. Do not leave a long rat hole.

2. Ream with circulation through casing shoe and areas where there is open hole cement.

3. Attempt to clean cement in the annulus prior to drilling.

4. Wait long enough for the cement to set before drilling ahead.

5. Minimize tripping speed when BHA passes through casing shoe or cement plug/cement squeeze depth.

References

John Mitchell Drilbert Engineering, 2002. Trouble-Free Drilling Volume 1: Stuck Pipe Prevention. Edition. Drilbert Engineering Inc.

Fanarco.net. 1999. Stuck Pipe Prevention Self-Learning Course. [ONLINE] Available at: http://www.fanarco.net/books/drilling/stuck-pipe.pdf. [Accessed 21 June 2016

Steve Devereux, 2012. Drilling Technology in Nontechnical Language, 2d Ed.. 2 Edition. PennWell Corp.